Moving image sequences may include multiple, sequential frames. Some modern image processing applications use estimates of motion in the images of moving image sequences. As used herein, the terms ‘motion estimates’ and ‘motion estimation’ refer to such estimates of motion. Motion estimates include parameters that describe motion between frame regions in segments of frames of a moving image sequence.
Image processing applications may estimate motion associated with various regions of the image frames of the moving image sequences. Applications may include or involve video compression, which relates to reducing the amount of data with which visual information is stored and conveyed (e.g., encoded, transmitted, received and decoded).
Motion estimates are a technique with which video compression applications achieve significant reduction in the data needed to represent image frames in moving image sequences. Applications may attempt to map, from one frame of a moving image sequence to another, translational or other motion of image regions within each of the frames. For instance, given a reference frame ‘A’ and a motion map that describes image motion from frame A to a subsequent frame ‘B’, a motion-predicted frame B can be formed by projecting the motion map from frame A. A difference frame B can be formed by subtracting the motion-predicted frame B from frame B.
Compression is achieved when the amount of data needed to encode both the motion map and the difference frame B is less than the amount needed for encoding frame B directly. Thus, an application may seek a motion map that yields a motion-predicted frame B that differs relatively little from frame B. For compression related purposes, the accuracy with which the motion map represents the actual motion of image features in the moving image sequence may not be a primary consideration. In other words, from the perspective of achieving compression, it may suffice that a given motion map simply reduces the amount of data needed to encode the motion map and the difference frame B.
Applications that use motion estimation may align an image feature, which appears in each of multiple frames of a moving image sequence, to a reference. A region of each frame in which the image feature appears is moved according to the motion estimate. The resulting set of image feature-aligned regions may then be blended, e.g., according to a formula. Accurate motion estimation can be important for accurately positioning feature-aligned regions between various frames of a moving image sequence.